Hospital officials expect the H1N1 virus to affect as many as 30 percent of the population in the Portland area.

Hospital officials said in a press release that people under 25 are at least four times as likely to get H1N1 as people ages 25 and older. A person with H1N1 can be contagious for up to 24 hours before they show any symptoms.

In addition, statistics show that pregnant women are very vulnerable to H1N1. While they make up only 1 percent of the population, they account for 6 percent of all H1N1-related deaths

The restrictions include: Visitors 18 or younger will limited to visiting only immediate family members; 18 or younger visitors will not be allowed into intensive care or family birth centers; only two immediate family members or support persons can accompany pregnant women during delivery and hospital stay.

The hospital will ask patients and visitors with respiratory symptoms to wear a mask that can be removed in a private room as long as they don't have flu-like symptoms such as sneezing, coughing or fever.

The restrictions, which took effect Monday, will be posted on signs at all six Legacy Health centers in the Portland area.

The hospital system is the second in the area to take precautions against the swine flu. OHSU hospitals has also placed restrictions on visitors.